Beijing expressed "regret" yesterday at South Korea's expansion of its air defence identification zone (ADIZ) in the East China Sea, weeks after China provoked regional fury by creating its own.

South Korea is expanding its air defence zone by about 66,500 square kilometres, roughly two-thirds the size of the country. It ill cover a submerged rock claimed by Seoul as well as Beijing.

Foreign ministry spokesman Hong Lei said the government was disappointed by the move and would continue to discuss the issue with the Republic of Korea, as South Korea is formally known.

"China expresses regret over the ROK's decision to expand its ADIZ," Hong said. "China will stay in communication with the ROK based on equality and mutual respect. We hope that the ROK will meet China halfway.

"Suyan is a submerged reef. It is not a territory. China and ROK have consensus on that. The relevant issues can only be solved through negotiation of maritime demarcation," he said.

Meanwhile, Tokyo cautiously endorsed South Korea's expanded zone, saying it had criticised a similar move by China because it covered Japanese territory. Japan's chief cabinet secretary Yoshihide Suga said Seoul had informed Tokyo in advance about its plans, something Beijing had not done.

"We don't think it's going to be a problem at the moment," said Suga, the government's top spokesman. "It is different from the one announced by China because it does not cover our country's territorial air, waters or land."

The mainland's state-run media played down South Korea's move. The Chinese-language edition of the Global Times, which normally strikes a nationalist tone, said in an editorial: "China will not make a big deal out of this right now."

South Korea's move to extend its air zone, the first revision to its air defence area in 62 years, was "opportunistic" in light of the more serious stand-off between Beijing and Tokyo, it said, but "China respects Korea's interests".

"Korea is a friendly and important partner in China's development," it said. "Hopefully Korea will fully respond to China's goodwill, not go over the line."

No editorials on the subject appeared in other major outlets, including the Communist Party paper, the People's Daily, or Xinhua, while other reports on the news were mild.